Vertebroplasty: an update

Vertebroplasty is a minimally invasive, image-guided injection of Polymethyl Methacrylate cement to relieve pain from a vertebral body fracture. It was described by Galibart et al1 in the treatment of spinal hemangiomas, other indications have emerged with experience. Perceived advantages of vertebroplasty is it increases patient mobility, decreases narcotic needs, and prevents further vertebral collapse.

Indications:1. Osteoporosis:
A 2007 study claimed that an estimated 1.7 million vertebral compression fractures occur every year in Europe and the United States. These osteoporotic fractures can sometimes be detrimental to function with regards the activities of daily living due to pain in the older patients.

While each patient's situation is different, the two most frequently debated interventions are vertebroplasty and kyphoplasty for symptomatic vertebral compression fractures. Long-term comparison studies are still underway for both procedures.

The VERTOS study prospectively compared osteoporotic compression fracture treatment of 18 patients with vertebroplasty to 16 patients with optimal medical management2. This study found significant short-term improvement in pain relief and function in the vertebroplasty group.

Alvarez, et al3 reported in a retrospective review of outcomes following vertebroplasty in an effort to define predictors of good outcomes in patients treated with this procedure. In 278 patients treated with vertebroplasty for 423 fractured levels between 1994 and 2002, multivariate analysis showed a correlation of the best outcomes with the following factors: two or fewer vertebral compression fractures; ASA 1 (American Society of Anesthesiologists grading for fitness for surgery); signal change on MR imaging (recent fracture); and collapse of less than 70% of Vertebral body height.

McGraw, et al4 prospectively evaluated 100 patients undergoing vertebroplasty for osteoporotic vertebral compression fractures at 156 levels (68 thoracic and 88 lumbar) over a 35-month period. In this group, 97% of patients reported significant pain relief at 24 hours that was sustained for a mean follow-up duration of 21 months. The pain scores dropped from 8.9 to 2.0 post-procedure, and 93% of patients noted an increased activity level. There were two complications, a sternal fracture and a transient radiculopathy.

Cooper and colleagues9 noted that 84% of vertebral compression fractures were associated with pain and it usually lasts four to six weeks, and is intense at the fracture site. Chronic pain often occurs when one level is greatly collapsed or when multiple levels are collapsed.

Ideal candidates for vertebroplasty are patients with activity-related axial pain corresponding to the level of a recent compression fracture, and this pain lessens or disappears completely with recumbency and/or sitting still. Many clinicians use tenderness over the appropriate level as an indication for vertebroplasty, although Gaughen, et al.10 analysed a series of 90 patients undergoing vertebroplasty and found 10 who had experienced no tenderness pre-operatively.

However, two widely discussed level one studies in NEJM comparing vertebroplasty to sham procedures demonstrated no significant improvement with vertebroplasty.5,6 This mixed evidence has sparked considerable debate as to the appropriate role of this procedure.

Another RCT recently published in Lancet, VERTOS II study, shows that the vertebroplasty performed six weeks following the osteoporotic compression fracture resulted in greater pain relief than the conservative treatment. The difference between groups in reduction of mean VAS score from baseline was 2.6 at one month and 2.0 at one year. No serious complications or adverse events were reported7,8.

Controversy remains with above mentioned NEJM studies. Although they describe about the same procedure, they do not necessarily address the same group of patients. The acuity of the fracture, the determination of intra-vertebral mobility or instability and possible concomitant diseases were not clearly defined or were not within a well-defined range.

Both studies have included the patients with symptoms up to one year duration and one study have used four weeks of mandatory medical treatment and excluded inpatients who actually might benefit from vertebroplasty5. There is also high crossover rate in both the studies.

In contrast VERTOS II study showed statistically significant improvement in pain relief initially and at one-year when performed at six weeks, though the controversy remains in the methodology as there was no blinding or concealment of allocation in the groups.

Recently, largely based on NEJM studies, The American Academy of Orthopaedic Surgeons (AAOS) recommend against the procedure for patients who present with an osteoporotic spinal compression fracture on imaging with correlating clinical signs and symptoms and who are neurologically intact11. The guideline mentions viable alternatives to vertebroplasty, such as calcitonin or facet blocks. In UK, National Institute of Clinical Excellence (NICE) guideline were issued in 2003, which support the usage of vertebroplasty in osteoporotic fractures, these guidelines have not updated12.

2. Tumours
In theory vertebroplasty improves both the strength and stiffness of abnormal bone and this has been demonstrated in cadaveric studies with as little as 2ml injection of cement13. In another study in which the authors used a finite-element model analysis, found that filling the vertebral body to within only 2% of its capacity restores vertebral stiffness to within 15% of the initial value14.

The release of chemical mediators, increased pressure within the bone, microfractures, the stretching of periosteum, reactive muscle spasm, nerve root infiltration and compression of nerves by the collapse of vertebrae are the possible mechanisms of malignant bone pain along with bony destruction. It is likely that a component of the vertebroplasty-related analgesia is secondary to immobilisation of micro-fractures and reduction of mechanical forces15.

The destruction of nerve endings by the cytotoxic, mechanical, and vascular effects of PMMA as well as the thermal effects of polymerisation, may also play a role in pain relief. Also PMMA has an anti-tumoral effect, which may explain the rarity of local recurrence after vertebroplasty16,17. Significant improvements in pain relief and QOL were initially demonstrated in more than 80% of their patients. Long-term follow-up evaluation revealed that pain control lasted in two thirds of these patients.

Cortet, et al.18, have reported a decrease in pain within 48 hours of vertebroplasty in 97% of their 37 patients with osteolytic metastases or multiple myeloma; pain was completely absent in 13.5%, significantly reduced in 55%, and moderatedly reduced in 30%. Beneficial effects were seen in 89% at three months and 75% after six months. Their complication rate was 2 to 3%. Fourney et al.19 reported on the treatment of tumorous lesions with VP and kyphoplasty in patients undergoing 65 vertebroplasties and 32 balloon kyphoplasties.

They have reported complete pain relief after 49 procedures (84%), and no change after five procedures (9%). The median pre- and postoperative VAS scores were 7 and 2, respectively (p<0.001). Pain reduction remained significant at each follow-up interval through one year (p=0.02). The mean percentage of restored vertebral body height was 42±21%. Mean improvement in local kyphosis was 4.1±3.72°.

Vertebroplasty is useful in patients with limited anticipated survival, poor surgical candidates, who have received maximum radiation doses, those with significant asymptomatic vertebral collapse secondary to a lytic lesion20, and also can be used as adjuvant to surgical fusion or radiotherapy. There is no controversy surrounding the usage of vertebroplasty in metastatic vertebral body tumours, myeloma and painful hemangiomas.

Conclusion:
In the current scenario usage of vertebroplasty for osteoporotic compression fractures is highly controversial with very little convincing evidence. The question still remains: Are there sub-populations and scenarios where vertebroplasty should be the procedure or treatment of choice? Ideal level 1 studies with proper patient selection criteria are lacking and current available evidence and guidelines remain controversial.

However vertebroplasty is an useful procedure in metastatic tumours, myeloma and painful hemangiomas, may suffice as an alternative to a large anterior procedure and offer adequate pain relief and stability.